1. Field of the Invention
The present invention is broadly concerned with improved wheat-derived components or products which are mixed with a source of Zn.sub.+2 and/or Al.sup.+3 ion to alter the properties thereof. More particularly, the invention pertains to such products, and particularly noodles, pastas, doughs and gluten, which are essentially free of chlorophyll and are preferably treated with zinc chloride and/or aluminum sulfate in order to overcome characteristic browning and/or create novel products.
2. Description of the Prior Art
One common type of food spoilage is caused by enzymatic browning. Perhaps the most well-recognized instance of enzymatic browning occurs when fruits or vegetables are cut, bruised or diseased. The disruption of the native structure allows phenolic compounds to combine with native phenolase enzyme which, in the presence of air, rapidly oxidizes the phenolics and causes tissue darkening.
Enzymatic browning of wheat-based foods or components is less well-recognized, but is common nevertheless. The appearance of noodles, pastas, wheat gluten and raw doughs such as biscuits and rolls are all affected by the extent of browning during processing and storage. The bran content of such products contains a high concentration of the phenolase enzyme polyphenol oxidase (PPO), which catalyzes enzymatic browning, particularly in noodles and pastas. While all noodles and pastas suffer from browning discoloration, the problem is especially severe with raw noodles and pastas, which are valued for their unique flavor. Storage of these raw products at room temperature or at refrigerator temperatures causes their color to darken. One response to this problem is to produce noodles and pastas from expensive low extraction flours or well purified farinas and semolinas, which minimizes bran content. However, use of such starting materials significantly increases costs and does not entirely eliminate the problem.
Other dough products which are subject to darkening include raw doughs for biscuits and rolls which are usually refrigerated. Use of the expensive flours commonly used for noodles and pastas is not a realistic alternative for these dough products.
Wheat gluten is the natural protein derived from wheat or wheat flour. When ground wheat kernels (wheat flour) are mixed with water, two native proteins (glutenin and gliadin) combine to form a viscoelastic mass called gluten. Commercial wheat gluten is generally obtained by first forming a flour/water dough or a sheared slurry of flour. The dough is kneaded and washed with copious amounts of water to give a starch-rich slurry and a residual cohesive mass of wet gluten. Alternatively, the sheared slurry of flour is centrifuged to produce A-starch and a protein-concentrate phase, which is further processed to produce B-starch and agglomerated gluten particles that are collected on screens. In either process the resultant gluten mass is carefully dried by spray- or flash-drying methods. Freeze-drying of gluten is used in the laboratory, but is too costly for commercial use.
Dry vital wheat gluten is a free-flowing light tan colored powder containing 75-80% protein. Enzymatic browning is one cause of darkening of wheat gluten, while another is absorption of endogenous flour pigments by the gluten proteins. The dark color of gluten is a problem both with the gluten itself and in certain gluten-supplemented foods, such as extra white rolls, restructured fish and meats, and vegetarian analogs.
A related problem with conventional gluten processing stems from the fact that it is difficult to disperse in water. Oftentimes, volatile acids or bases assist in gluten dispersion; however, those additives remain as impurities in the dried gluten and can affect the flavor, odor or other properties of the final product. Additionally, the vapors from the gluten dryer contain potential pollutants.
The prior art describes the addition of zinc to white flour for nutritional purposes, and one report on the attempted oxidation of bread dough with zinc ion. P. Ranum, Cereal Chem 57:70 (1980) reported that 1.65-1.90 mg of zinc must be added to 100 g (14% m.b) of different flours to achieve the target level of 2.2 mg total zinc per 100 g flour. S. H. Rubin, A. Emodi, and L. Scialpi, Cereal Chem 54:895 (1977) and A. S. Emodi and L. Scialpi, Cereal Chem 57:1 (1980) concluded it was technically feasible to fortify bread with zinc with the target level of zinc added to flour of 2.2 mg/100 g, which was proposed by the Food and Nutrition Board of the National Academy of Sciences in 1974. The target level of fortification is equivalent to .about.4.6 mg zinc chloride per 100 g of flour, which is on the order of 0.002% by weight Zn.sup.+2, based upon the weight of the wheat flour taken as 100%. K. Finney, B. L. Bruinsma, and O. Natsuaki, Cereal Chem 69:347 (1992) reported that zinc ion at 0.02-2.4 mg/100 g flour-failed to improve bread volume and crumb grain.
U.S. Pat. No. 4,840,808 describes a method for color preservation of vegetable pasta products wherein fresh green vegetable matter is treated with an aqueous alkaline solution to hydrolyze the methyl and phytyl ester groups of the chlorophyll content thereof, followed by mixing the vegetable matter with flour and selected metal ions including zinc and aluminum cations, and extruding the blend to create a pasta product.
Baking powders are used to produce a number of leavened bakery foods, including layer cakes, chiffon cakes, cake donuts, quick breads, biscuits, muffins, tortillas, pancakes and waffles. They are also used to produce self-rising flour.
Baking powders are mixtures of sodium bicarbonate and a leavening acid, which may be one of eight compounds or mixtures thereof (E. J. Pyler, "Baking Science and Technology", 3rd Ed., Sosland Publishing, Merriam, Kans., 1988, pp. 928-931). Sodium bicarbonate dissolves readily in a batter or dough at room temperature, but the various leavening acids dissolve at different rates during mixing, make-up and cooking of the batter or dough. Fast-acting baking powders release practically all their carbon dioxide during the mixing step, whereas slow-acting baking powders act during the cooking step. Double-acting baking powders release some of their carbon dioxide during mixing, and the remainder during baking, frying or griddling.
Acidic sodium aluminum phosphate (SALP) and sodium aluminum sulfate (SAS) are chemical leavening acids that dissolve poorly in doughs or batters at room temperature, but are soluble at cooking temperatures. These slow-acting leavening acids often constitute approximately one-fourth the weight of a double-acting chemical leavening agent, i.e., baking powder. The only other commonly used slow-acting leavening acid is sodium acid pyrophosphate (SAPP).
Baking powders are used usually between 1% and 7% based on flour, which is equivalent to approximately 0.03-0.20 wt% aluminum ion based on flour (W. J. Sultan, "Practical Baking", 2nd Ed., AVI, Westport, Conn., 1959, p. 46) when the baking powder is double-acting and contains SALP or SAS.
There is accordingly a real and unsatisfied need in the art for an improved method to treat wheat-derived products so as to market brighter products with reduced brown or grey off-color. Additionally, there is a need for improved gluten processing techniques which avoid the use of volatile acids or bases.